Why response.write() is printing only the first row in node.js?

Question

Why response.write() is printing only the first row in node.js?

I am new in node.js . I am facing a problem with a GET request . I am using 2 mysql query. First one is returning some ids , I am using those Ids in my 2nd query . In the console all the rows are successfully printing but in the browser only the first row.

My Code structure is like :

function userProjects(request, response) {

    connection.query("1st query", function(err, first_output, fields) {
        response.writeHead(200, {
            "Content-Type": "application/json"
        });

        for (var i in first_output) {
            var obj = first_output[i];
            connection.query("select * from table where parent_id=" + obj.id, function(err, apartmentRows, fields) {
                console.log(apartmentRows);
                response.write("apartments are : " + JSON.stringify(apartmentRows));
                response.end();
            });
        }
    });
}

So far I have understood by surfing various contents ,due to response.end() it is stopping to get remaining rows here . That's why all are not printing . But I failed to figure out the solution to solve it .

Thanks in advance.

mysql
node.js

Answer 1

You will need to ensure that all of your queries get executed before calling response.end(). My naive approach would be to set a counter flag to check the number of queries performed. Once all the queries have been performed just end the response.

function userProjects(request, response) {

    connection.query("1st query", function(err, first_output, fields) {
        response.writeHead(200, {
            "Content-Type": "application/json"
        });
        var totalQueries = 0;
        for (var i in first_output) {
            var obj = first_output[i];
            totalQueries++; //increases the number of query performed
            connection.query("select * from table where parent_id=" + obj.id, function(err, apartmentRows, fields) {
                console.log(apartmentRows);
                response.write("apartments are : " + JSON.stringify(apartmentRows));

                totalQueries--; //decreases the query count 
                if (totalQueries == 0) //when all queries are performed end the response
                    response.end();
            });
        }
    });
}